JPH05194955A - Light intensity regulating material and light intensity regulating element containing the same - Google Patents

Abstract

PURPOSE:To obtain a light intensity, regulating material having good uniformity and excellent voltage sensitivity by mixing a liquid crystal with a polymeric substance comprising a specified (meth)acrylic acid copolymer. CONSTITUTION:A light intensity.regulating material which regulates the transmission and scattering of light according to the presence or absence of an applied electrical field and comprises a liquid crystal and a polymeric substance, wherein the polymeric substance is obtained by copolymerizing a photopolymerizable composition comprising at least two (meth)acrylic acid compounds, and at least one of the (meth)acrylic acid compounds is a fluoro(meth)acrylic acid compound. The use of the fluoro(meth)acrylic acid compound allows the above material to give the objective light intensity regulating element markedly improved in voltage sensitivity and reduced in driving voltage and to be one with particularly excellent uniformity and voltage sensitivity. The objective light intensity regulating element can be obtained by sandwiching this material between a pair of bases at least either of which contains a transparent electrode in its inside.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light control material and a light control element comprising the same.

[0002]

2. Description of the Related Art A light control material composed of a liquid crystal and a polymer material that holds the liquid crystal becomes cloudy because incident light is scattered due to a difference between the refractive index of the polymer material and the refractive index of the liquid crystal when no electric field is applied. Further, when an electric field is applied, the liquid crystal aligns in the direction of the electric field, and the refractive index of the polymer substance and the refractive index of the liquid crystal are close to each other, so that the liquid crystal becomes transparent. When the electric field is removed, the original cloudy state is restored.

Dimmer elements utilizing such properties have been reported in, for example, Japanese Patent Application Laid-Open No. 64-62615, Japanese Patent Application Laid-Open No. 2-502929, and Japanese Patent Application Laid-Open No. 1-252689. The light control element is required to have arbitrary transmittance, repetitive response, voltage sensitivity, response speed, film uniformity, light resistance, heat resistance, water resistance, etc. The device could not be said to have the characteristics satisfying these requirements.

[0004]

SUMMARY OF THE INVENTION The present invention solves the above problems and provides a light control material having particularly good uniformity and excellent voltage sensitivity, and a light control element using the same.

[0005]

The inventors of the present invention have conducted extensive studies to achieve the above-mentioned object, and as a result, as a polymer substance that holds liquid crystals in a light control material, a specific (meth) acrylic acid-based It has been clarified that the voltage sensitivity of the light control element is significantly improved and the voltage can be reduced by using the copolymer, and the present invention has been reached.

That is, the gist of the present invention is a dimming material which controls the transmission and scattering of light depending on whether an electric field is applied or not. The material includes a liquid crystal and a polymer substance, and the polymer substance comprises two or more kinds ( A polymer material obtained by copolymerizing a photopolymerizable composition comprising a (meth) acrylic acid compound, and at least one of the (meth) acrylic acid compounds is a fluorine-containing (meth) acrylic acid compound And a dimming element characterized by comprising the above dimming material sandwiched between a pair of substrates having electrodes on at least one of the transparent inner surfaces thereof. ..

The present invention will be described in detail below. The light control material of the present invention is composed of a liquid crystal and a polymer substance that holds the liquid crystal.
A polymer obtained by polymerizing a photopolymerizable composition comprising one or more (meth) acrylic acid-based compounds and having at least one of the (meth) acrylic acid-based compounds represented by the following general formula (1)

[0008]

Embedded image CH ₂ ═CR ¹ —COOR ² —----- (1) [wherein, R ¹ represents a hydrogen atom or a methyl group, and R ² is a fluorine atom-containing alkyl group having 1 to 18 carbon atoms. A fluorine-containing (meth) acrylic acid ester represented by

Examples of R2 include 2-fluoroethyl group, 2,2-difluoroethyl group, 1,3-difluoro-2-propyl group, 4,4,4-trifluorobutyl group, 2,2, 2-trifluoroethyl group, tert-trifluorobutyl group, iso-trifluoropropyl group, 2,2,3,3-tetrafluoropropyl group, 1H, 1H-pentafluoropropyl group, 1H, 1H, 9H-hexa Decafluoro-1-nonyl group, 2,2,3,4,4,4-hexafluorobutyl group, iso-hexafluoropropyl group, hexafluoro-2-methyl-iso-propyl group, 1H, 1H-heptafluoro group -1-Butyl group, 1H, 1H, 2H, 2H-heptadecafluorodecyl group, heptafluoro-2-pentyl group, 1H, 1H, 5H-octafluoro-1-pentyl group, 1H, 1H, 7H-dodecafluoro group -1
-Heptyl group, 1H, 1H, 11H-eicosafluoro-1-undecyl group, 1H, 1H, 7H-dodecafluoro-1-heptyl group, 1H, 1H-
Pentadecafluoro-1-octyl group, 1H, 1H, 2H, 2H-per
Examples thereof include a fluorododecyl group, a 1H, 1H, 2H, 2H-perfluorohexyl group and a 1H, 1H, 2H, 2H-perfluorooctyl group.

On the other hand, (meth) acrylic acid compounds other than the above fluorine-containing (meth) acrylic acid ester include (meth)
The acrylic acid ester compound (a) and the (meth) acrylic acid amide compound (b) are used, and the (meth) acrylic acid ester compound (a) is particularly preferable. Examples of the (meth) acrylic acid ester compound (a) include monofunctional to polyfunctional (meth) acrylic acid ester compounds having preferably 1 to 6 (meth) acrylic acid ester groups in the molecule.

As the monofunctional (meth) acrylic acid ester compound, linear or branched aliphatic alcohol, cyclohexanol, tetrahydrofurfuryl alcohol, ethylene glycol monoalkyl ether, polyethylene Glycol monoalkyl ether, Propylene glyco-
Rumonoalkyl ether, polypropylene glycol monoalkyl ether, 1,3-butylene glycol monoalkyl ether, tetramethylene glycol monoalkyl ether, hexamethylene glycol monoalkyl ether
(Meth) acrylates of monofunctional alcohols such as tell.

As the polyfunctional (meth) acrylic acid ester compound, ethylene glycol, propylene glycol, polypropylene glycol, which may be substituted with a lower alkyl group such as methyl group and ethyl group, Poly (meth) acrylate of diols such as 1,3-butylene glycol, tetramethylene glycol, hexamethylene glycol, etc., and polyols such as trimethylolpropane, glycerin, tetramethylmethane, etc. Kind of; Trimethylo-
A poly (meth) acrylate of polyol obtained by adding ethylene oxide or propylene oxide to isocyanuric acid or propane, tetramethyl methane, for example, tris-acryloyloxyethyl isocyanurate is used.

The monofunctional and polyfunctional (meth) acrylic acid ester compounds are preferably used as a mixture of two or more kinds. In particular, a monofunctional (meth) acrylic acid ester compound is difficult to form a film when used alone as a light control material, and it is preferably used as a mixture with a bifunctional or higher functional compound. In this case, the ratio of the former to the latter is usually 1 /
It is selected from the range of 10 to 10/1. The (meth) acrylic acid amide compound (b) is a monofunctional to difunctional compound having preferably 1 to 2 (meth) acrylic acid amide groups in the molecule.
Examples thereof include (meth) acrylic acid amide compounds.

The monofunctional (meth) acrylic acid amide compounds include acrylamide, methacrylamide; N-ethyl acrylamide, Nn-butyl methacrylamide, N-
N-alkyl substitution such as tert-butyl acrylamide, N, N-di-n-butyl acrylamide, N-octyl acrylamide
(Meth) acrylamides; N-methoxymethylmethacrylamide, Nn-butoxymethylmethacrylamide, N-
N-alkoxyalkyl substituted (meth) acrylamides such as iso-butoxymethyl acrylamide, N-iso-amyl acrylamide are used. Examples of the bifunctional (meth) acrylic acid amide compound include alkylenebis (meth) acrylamides such as hexamethylenebisacrylamide.

The monofunctional and difunctional (meth) acrylic acid amide compounds are preferably used as a mixture of two or more kinds, as in the case of the (meth) acrylic acid ester compound. In particular, a monofunctional (meth) acrylic acid ester compound is difficult to form a film when used alone as a light control material, and it is preferably used as a mixture with a bifunctional or higher functional compound. In this case, the ratio of the former to the latter is usually 1/1.
It is selected from the range of 0 to 10/1.

The fluorine-containing (meth) acrylic acid ester represented by the formula (1) in the photopolymerizable composition comprising two or more kinds of (meth) acrylic acid compounds constituting the light control material of the present invention is preferable. The proportion is from 1 to 90% by weight, and particularly preferably from 5 to 80% by weight, based on the total amount of the polymer substance.

As the liquid crystal in the light control material of the present invention,
Any of a nematic liquid crystal, a cholesteric liquid crystal, and a smectic liquid crystal can be used. The nematic liquid crystal can be selected in a considerably wide range as long as it exhibits a nematic state in the operating temperature range. Also,
A cholesteric state can be obtained by adding an optically active substance described later to such nematic liquid crystal. Examples of the nematic liquid crystal include the substances shown in Tables 1 to 3 below and derivatives thereof.

[0018]

[Table 1]

[0019]

[Table 2]

[0020]

[Table 3]

In the chemical formulas in Tables 1 to 3, R '
Represents an alkyl group or an alkoxy group, R represents an alkyl group, X ′ represents an alkyl group, an alkoxy group, a nitro group,
A cyano group, a trifluoromethyl group, a trifluoromethoxy group or a halogen atom is shown. Further, the benzene ring may be further substituted with a fluorine atom.

The liquid crystal used for the light control material of the present invention includes:
Any of the liquid crystals shown in Table 1 or a mixture containing them may be used. For example, ZLI-1132, ZLI-1 from Merck & Co., Inc.
840, a liquid crystal marketed under the trade name of ZLI-1565; E-7, E- from BDH (British Drug House)
8, E-37, E-44, E-46, BL001-BL
A liquid crystal or the like which is commercially available under the trade name of 020 is used.

A cholesteric state can be obtained by adding an optical rotatory substance to the above nematic liquid crystal. As the optical rotatory substance, a chiral nematic compound, for example, nematic liquid crystal, 2-methylbutyl group, 3-methylbutoxy group, 3-methylpentyl group, 3-methylpentoxy group, 4-methylhexyl group, 4-methylhexoxy group, etc. The compound having an optically active group introduced therein is mentioned. Further, as shown in JP-A-51-45546, alcohol derivatives such as 1-menthol and d-borneol, d-camphor, ketone derivatives such as 3-methylcyclohexane, d-citronellic acid, 1-camphor. Examples thereof include carboxylic acid derivatives such as acids, aldehyde derivatives such as d-citronellal, and other optically active substances such as amine, amide and nitrile derivatives. Furthermore, smectic A liquid crystals and smectic chiral C liquid crystals are used as the smectic liquid crystals in the light control material of the present invention.

In order to produce the light control material of the present invention, the above-mentioned liquid crystal, a photopolymerizable composition comprising two or more (meth) acrylic acid compounds, and a photopolymerization initiator may be mixed and used in some cases. It may be heated and exposed as a uniform solution. as a result,
The polymer substance produced by the copolymerization and the liquid crystal are in a phase separated state, and the light control material of the present invention composed of the liquid crystal and the polymer substance holding the liquid crystal can be obtained.

The ratio of liquid crystal in the above homogeneous solution is 4
It is 0 to 90% by weight, preferably 65 to 85% by weight. As the photopolymerization initiator, for example, 2,2-dimethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl
-1-Phenylpropan-1-one and the like are used. Further, if necessary, a surfactant, a light stabilizer, a dichroic or non-dichroic dye, a chain transfer agent, a photosensitizer, a cross-linking agent and the like can be used in combination.

In the light control device of the present invention, the above liquid crystal, a photopolymerizable composition comprising two or more (meth) acrylic acid compounds and a photopolymerization initiator are mixed to prepare a uniform solution, which is used as an electrode. It can be industrially advantageously manufactured by sandwiching it between substrates, exposing it to copolymerization and molding it into a film,
It is also produced by sandwiching a light control material obtained by previously copolymerizing a photopolymerizable composition containing the liquid crystal between substrates.

A transparent electrode such as ITO is used as the electrode of the light control element, and a glass or polyester plate is used as the electrode substrate. When a pair of transparent electrode substrates is used, it is used as a transmissive dimming element, and when one is transparent and the other is opaque, by placing a reflective layer after the opaque electrode substrate. It can be used as a reflection type light control device.

[0028]

EXAMPLES The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples as long as the gist thereof is not exceeded.

Example 1 As a photopolymerizable composition, 0.05 g of trimethylolpropane triacrylate, 0.05 g of n-butyl acrylate and 2,
2,2-trifluoroethyl methacrylate [R ¹ : CH ₃ , R ² : CH ₂ CF ₃ substance in the formula (1)] 0.05 g of a mixture was used,
To this, 0.003 g of 2,2-dimethoxy-2-phenylacetophenone (photopolymerization initiator) and liquid crystal E-8 (manufactured by BDH)
0.35 g was mixed to make a uniform solution.

In the above solution, a plastic (S
P-210, Sekisui Fine Chemical Co., Ltd.) Spacer 0.00
8 g was added, and this mixed solution was inserted between a pair of 6 cm × 9 cm size plastic plates with ITO (polyethylene terephthalate with a thickness of 125 μm), and it was cracked by exposing with an ultraviolet irradiation device. A uniform light control element having no light was obtained. The applied energy corresponds to 800 millijoules (mJ).

When a voltage is applied to the light control element thus obtained, the liquid crystal molecules in the light control material in the random state are aligned, and the light control element itself changes from an opaque state to a transparent state. In particular, when an AC voltage of 100 V (V) (60 Hz. Sine wave, the same in the following examples) is applied, the light transmittance reaches saturation, and when viewed at a wavelength of 600 nm, the transmittance is 78%. there were. To obtain 90% transmittance when 100V is applied, 1
An applied voltage of 9V was required.

Comparative Example 1 Cracking was performed in the same manner as in Example 1 except that a mixture of 0.05 g of trimethylolpropane triacrylate and 0.10 g of n-butyl acrylate was used as the photopolymerizable composition. A uniform light control element having no light was obtained. 100 in the obtained dimming element
When an AC voltage of V was applied, the light transmittance reached saturation, and when viewed at a wavelength of 600 nm, the light transmittance was 80%. Further, an applied voltage of 60 V was required to obtain 90% of the transmittance when 100 V was applied, which was inferior to that of Example 1.

Example 2 As a photopolymerizable composition, tris-acryloyloxyethyl isocyanurate 0.05 g, n-butyl acrylate 0.1 g.
05 g and 2,2,2-trifluoroethyl methacrylate 0.05
The same procedure as in Example 1 was carried out except that the mixture of g was used to obtain a uniform light control element without cracks. When an AC voltage of 100 V was applied to the obtained light control device, the light transmittance reached saturation, and when viewed at a wavelength of 600 nm, the light transmittance was 77%.
19V is required to obtain 90% of the transmittance when 100V is applied.
Applied voltage was required.

Example 3 As a photopolymerizable composition, 0.05 g of tris-acryloyloxyethyl isocyanurate, n-butyl acrylate was added.
08 g and 1H, 1H, 2H, 2H-heptadecafluorodecyl acrylate [R ¹ : H, R ² : CH ₂ CH ₂ C ₈ F ₁₇ substance in formula (1)] 0.02
The same procedure as in Example 1 was carried out except that the mixture of g was used to obtain a uniform light control element without cracks. When an AC voltage of 100 V was applied to the obtained light control device, the light transmittance reached saturation, and when viewed at a wavelength of 600 nm, the light transmittance was 80%.
In addition, 34V is required to obtain 90% of the transmittance when 100V is applied.
Applied voltage was required.

Comparative Example 2 As a photopolymerizable composition, 0.05 g of tris-acryloyloxyethyl isocyanurate and n-butyl acrylate were used.
The same procedure as in Example 2 was carried out except that 0.10 g of the mixture was used to obtain a uniform light control element without cracks. When a 100 V AC voltage was applied to the light control device thus obtained, the light transmittance reached saturation, and when viewed at a wavelength of 600 nm, the light transmittance was 81%. Further, an applied voltage of 40 V was required to obtain a transmittance of 90% of the transmittance when 100 V was applied, which was inferior to that of Example 2.

Example 4 As a photopolymerizable composition, 0.04 g of trimethylolpropane triacrylate, 0.05 g of tetraethylene glycol diacrylate, 0.05 g of tetradecaethylene glycol diacrylate and 1H, 1H- Heptafluorobutyl acrylate [R ¹ : H, R ² : CH ₂ C ₃ F _{7 in} the formula (1)] A crack was prepared by treating in the same manner as in Example 1 except that a mixture of 0.05 g was used. A uniform light control element having no light was obtained. 100 in the obtained dimming element
When an AC voltage of V was applied, the light transmittance reached saturation, and when viewed at a wavelength of 600 nm, the transmittance was 73%. Also, an applied voltage of 53 V was required to obtain 90% of the transmittance when 100 V was applied.

Comparative Example 3 In the photopolymerizable composition used in Example 4, 0.05 g of tetradecaethylene glycol diacrylate was used instead of 0.05 g of 1H, 1H-heptafluorobutyl acrylate. The same photopolymerizable composition as in Example 4 was used, and the same treatment as in Example 4 was carried out to obtain a uniform light control element without cracks.
When an AC voltage of 100 V was applied to the obtained light control element,
The light transmittance reached saturation, and at a wavelength of 600 nm, the transmittance was 75%. In addition, the transmittance of 90 when applying 100 V
The applied voltage of 78 V was required to obtain the percentage, which was inferior to that of Example 4.

[0038]

The light control material of the present invention has good film uniformity, and the light control element using this light control material has excellent voltage sensitivity and is useful as a display device, a light control window, and the like.

Claims (3)

[Claims] 1. A light control material for controlling transmission / scattering of light according to whether or not an electric field is applied, the liquid crystal and the polymer substance being contained, and the polymer substance is two or more kinds of (meth) acrylic acid compounds. Is a polymer substance obtained by copolymerizing a photopolymerizable composition consisting of the compound (1) and at least one of the (meth) acrylic acid compound is a fluorine-containing (meth) acrylic acid compound. Light material. 2. A fluorine-containing (meth) in claim 1 acrylic compound has the following general formula (1) ## STR1 ## _{^{CH 2 = CR 1 -COOR 2 ------}} (1) [ In the formula, R ¹ represents a hydrogen atom or a methyl group, and R ² represents a fluorine atom-containing alkyl group having 1 to 18 carbon atoms]. The light control material according to claim 1. 3. A polymer substance containing a liquid crystal and a polymer substance, wherein the polymer substance is obtained by polymerizing a photopolymerizable composition comprising two or more (meth) acrylic acid compounds. And at least one of the (meth) acrylic acid-based compounds is a fluorine-containing (meth) acrylic acid-based compound sandwiched between a pair of substrates having electrodes on at least one of which is transparent. A light control element characterized by the above.